The present invention is directed to a solenoid valve, the solenoid valve comprising an input port including an input sealing tip which is spring biased for closing it, a first output port, and a second output port to the environment including an output sealing tip which is spring biased for closing it, and a solenoid coil arrangement for selectively generating magnetic fields which result in a force either on the input sealing tip to pull it away from the input port for opening it or a force on the output sealing tip to pull it away from this second output port for opening it. In particular the present invention is directed to a solenoid valve for controlling inflation and deflation of an air cell in a vehicle seat, the input port of the solenoid valve being adapted for connection to a source of pressurized air and the first output port being connected to the air cell.
Drivers and passengers of motor vehicles, especially when driving long distances, often experience discomforts caused by long time static posture when seated in a vehicle seat. This is not only felt as being uncomfortable and causing for example back pain but may also lead to permanent impairment of health, in particular for professional drivers such as taxi, truck and bus drivers. To provide a remedy the automotive industry since sometime offers vehicle seats with adjustable lumbar air supports and bolsters and with integrated massage systems in the seat back. The lumbar supports and bolsters in the seat are adjusted by inflating air cells by inflating them with pressurized air and closing them in the desired state. In massage systems series of air cells are sequentially inflated and deflated to provide a massage effect.
Valves are used to control the air supply to the air cells in the vehicle seat. For the lumbar supports, side supports and bolsters valves of the normally closed type are utilized. Such normally closed valves have two independently controllable valve elements for selectively either opening input port to let pressurized air to a first output port connected to the air cell, or by connecting a second output open to the environment so that pressurized air can flow out of the air cell for deflating it. In the inactivated state the input port and the second output port to the environment are closed. The solenoid valve of the present invention is of the normally closed type and is therefore rather suitable for application in connection with lumbar supports, side supports and bolsters and the like. However, in principle the valves of the present invention can also be utilized in massage systems for vehicle seats.
A solenoid valve comprising the features of the preamble of claim 1 is described in WO 2013/011340 A1. The solenoid coil arrangement comprises two coaxially disposed solenoid coils. In each of the adjacent solenoid coils a moveable plunger is received. If the first solenoid coil is activated by supplying voltage its plunger is moved in an axial direction of the coil in the direction towards the end adjacent to the other solenoid coil. If the opposite second solenoid coil is activated to generate an oppositely directed magnetic field the plunger of the second solenoid coil is moved in axial direction of the second solenoid coil in the direction to-wards its end adjacent to the first solenoid coil. The first plunger is connected to an input sealing tip which is spring biased to seal the input port of the valve, and the second plunger to an output sealing tip which is spring biased to seal the second output port of the valve to the environment. By energizing the first solenoid coil the plunger is moved further into the first solenoid coil and thereby also moves the input sealing tip away from the input port of the valve to open it, and by energizing the second solenoid coil its plunger is moved further into the second solenoid coil which in turn moves the output sealing tip away from the second output port to open it to the environment.
Such an arrangement is schematically shown in FIG. 13. The solenoid valve comprises a sealed housing 100 in which a first solenoid coil 101 and oppositely and coaxially to it a second solenoid coil 111 is arranged. The first solenoid coil 101 is surrounded by an iron frame 103. In the interior of the first solenoid coil 101 an iron plunger 102 is ex-tending which is connected to an output sealing tip 105. A spring 104 is acting on the iron plunger 102 such that the output sealing tip 105 is pressed into its sealing position closing the second output port. Likewise the second solenoid coil 111 is surrounded by an iron frame 113, and is provided with an iron plunger 112 which is spring biased by spring 114 acting on it such that an input sealing tip 115 carried at its outer end is pressed onto the input port of the valve housing 100 to close it. The two solenoid coils 101 and 111 are operated independently. In operation, only one of the two solenoid coils is activated at a time. When the first solenoid coil 101 is activated by supplying voltage to it the magnetic field generated results in a force on the iron plunger 102 such that it is moved against the bias force of the spring 104 to move further into the interior of the first solenoid coil 101. In this situation the second output port of the valve is opened such that pressurized air can flow through the first output port connected to the air cell and through the valve housing to the second output port and to the environment to deflate the air cell. If in turn the second solenoid coil 111 is activated, while the first solenoid coil 101 remains inactivated, the magnetic field generated by the second solenoid coil draws the iron plunger 113 further into the interior of the second solenoid coil 111 such that the input sealing tip 115 carried at the outer end of the iron plunger 113 is lifted off the input port of a valve housing 100 such that pressurized air may flow through the housing to the first output port connected to the air cell for inflating it. For operating the valve, in principle a voltage supply delivering voltage of a single polarity is sufficient since the terminals of the solenoid coils may be connected such that they generate of opposite polarity.